I know some press owners have instructed authors not to communicate with watchdog sites or included non-disparagement and other clauses into author's contracts that prevent this. Or reference might be made to sales figures being "confidential"--which they are: to the author. This means the author can usually choose to disclose them to whomever they wish. Of the 63 epublishers currently listed only a handful are well represented in the EREC dataset. And in order to provide publisher-specific data I need a bare minimum of 5 books by 3 different authors from that press--preferably a lot more.
I would like to give a shout out to those who have reported data in the past. If you look at the graph below, relating to sales achieved by ebooks that have been on sale one year or more, you can see the dataset is dwindling a bit. In order to fairly reflect the sales of presses whose performance is improving I count only data for book that was reported within last last 365 days. The yellow arrows show epublishers that have dropped from the publisher-specific data set due to lack of data. If you have sales data you could add, or update, I would really appreciate it.